The invention relates to methods of minimizing disease transmission by used hypodermic needles, and hypodermic needles adapted for carrying out the methods.
Known hypodermic needles typically have (a) a sharp point to facilitate penetration of the skin, a bottle top or an injection port; and (b) an open tip to allow for injection and withdrawal of fluid. Typically such needles have cutting points, formed by a beveled cut with an opening created at the junction of the beveled edge and the needle bore.
FIGS. 1a-1c respectively show intradermal, short, and regular needle points, the basic types currently available from Becton-Dickinson, the largest manufacturer.
Unfortunately, these features pose a threat to anyone who comes into contact with a used needle. The sharp point increases the likelihood of skin puncture. The open tip can house infected fluid or tissue and thereby transmit disease to an individual who subsequently is exposed to the needle.
These features have the most significant consequences for individuals exposed to human products in environments where hepatitis and AIDS are of paramount concern. Transmission of malaria, treponema pallidum, Rocky Mountain spotted fever, tuberculosis, toxoplasmosis, blastomycosis, cryptococcosis, brucellosis and leptospirosis by infected needles also has been reported; hence there also is concern among individuals working in veterinary practices and research laboratories. These risks can be extended to the general public through improper needle disposal, illicit use of needles, etc.
The multiple sources of needle stick injury indicate that there is no single remedy. In a recent study, Jagger et al. (N Engl J Med 319:284-288, 1988) noted that one third of the 326 needle-stick injuries reported in a university hospital in a ten-month period were related to recapping. Needles inserted into intravenous tubings had the second highest rate of injury as a result of intentional and inadvertent detachment. The authors concluded that:
Each device that causes such PA1 Try to gown, glove, double boot
injuries must be modified according
to its specific use and handling
requirements . . . . To provide the
greatest benefit, the safety feature
should be an integral part of the
device and not an accessory to be
used in combination with a hazardous
item. In this way, it is certain to
be available precisely when and where
it is needed. Moreover, the safety
feature should be in effect before
disassembly and should remain in
effect after disposal, thus
protecting the trash handler as well
as the user. Finally, safety features
should be as simple as possible and
should require little or no training
to use effectively. [N. Eng. J. Med.
319:284-288, 1988.]
The problem was addressed in Newsweek, in an article entitled "A Very Risky Business" (Nov. 20, 1989). In response to this article, a reader wrote:
. . while a patient is extubating
himself from a ventilator, or pulling
out his i.v. lines, or is in cardiac
arrest. The reason adequate
precautions receive such a low
compliance is not from lack of a
desire to implement them but because
in a few precious moments one must
act quickly to protect the patient
from known harm, not oneself from
potential harm. [Makar, E. V., Letter
to Editor, December 18, 1989.]
Such scenarios contribute to more than 800,000 accidental needle sticks each year.
Recent attempts to address the problems associated with recapping have included:
a) incorporating a plastic casing that is advanced over the needle tip automatically as a catheter is slipped over a needle to be placed in a vessel (Critikon, Inc. 1990).
b) incorporating a plastic casing which is manually advanced from around the syringe barrel to beyond the needle tip such that recapping is less likely to be associated with inadvertent skin puncture (Becton-Dickinson, Inc. 1990).
c) recapping needles in a special adaptor which is secured to a table top rather than in a traditional cap which is held in one's hand (Goldman, U.S. Pat. No. 4,836,373).
d) providing guidance grooves in the cap to facilitate safe needle entry (Bennett, U.S. Pat. No. 4,419,098).
The disclosures of these references and all other prior art information mentioned herein are expressly incorporated by reference.
Certainly, the aforementioned devices might provide added safety. However, they are not foolproof. In addition, in many cases, they entail the use of far more plastic (with increased cost of manufacture and environmentally safe disposal), are more bulky than traditional devices, entail modifications of one's usual practices, may not be adaptable to all sizes of needles and syringes, and may not be universally applicable to the varied settings where needle sticks commonly occur.
In many settings, one tries to avoid the use of needles altogether when adding medications or supplemental fluids to an already existing intravenous line (as would be the case for all intraoperative patients and many other hospitalized patients). This commonly is accomplished by adding stopcocks to the intravenous tubing. However, typical stopcocks have certain limitations: (1) they generally can allow flow through either the main line or the sideport, but not through both simultaneously; (2) when the protective covering, syringe or tubing is removed from a port of the stopcock, this port may no longer be sterile and hence is a potential source of patient contamination; and (3) most intravenous tubing does not come with stopcocks in place (cost, bulkiness, risk of disconnect with leakage or blood loss, risk of patient contamination).
These limitations have led to the design of systems which entail modifying the male and female connectors such that the cannula pierces the diaphragm without the use of a needle (InterLink IV Access System, Baxter Healthcare Corp., 1990). Limitations of such modifications include: need to modify one's practices to use bulkier setups, increased cost, and need for increased use and disposal of plastic. Furthermore, the use of this system requires modification or replacement of existing setups, so that a matched cannula and diaphragm will always be available.
As a compromise, systems have been designed with plastic casing which extends around and beyond the needle shaft and tip. This fits into a matched receptor at the penetrable diaphragm of a bottle, tubing, etc. (Ogle, U.S. Pat. No. 4,834,716 produced as Stick-Gard Safety Needle by International Medical Systems, Limited 1990). These have not gained widespread acceptance because of many of the aforementioned limitations. Furthermore, these setups are not fool-proof, in that one can still contact a contaminated needle.
We conclude that needles probably are here to stay. While healthcare workers are eager to see the risks associated with needles eliminated, they also would prefer not to markedly change their practices. Changes in themselves may be associated with risks, in addition to increased cost and potential compromises in patient care. Furthermore, there are settings where the use of needles appears to be unavoidable, e.g., injections, blood withdrawal, and intravascular catheter insertion.
Thus, a major priority should be a method of providing needles so that they can be handled more safely. Even though a needle stick cannot totally be avoided, we believe that the consequences of such a stick can be decreased markedly if a needle with one or more recessed orifices on its shaft and/or taper is employed. In addition to the needles of the present disclosure themselves being inherently safer, they offer the additional advantage of facilitating the use of such safety features as the protective sheaths and caps described herein.
To date, all reported transmissions of AIDS via puncture wounds to health care workers have resulted from puncture with a hollow bore device such as a traditional hypodermic needle or a broken glass tube. These present a sizeable inoculum which may be avoided with the solid-tip needles described herein. Although solid-tip needles are commercially available from many manufacturers for use in spinal myelography and soft tissue biopsy, and perineural injections, as shown in FIG. 2, the art has recognized neither the methods nor the apparatus disclosed herein, nor their advantages.
A typical needle includes four integral elements: a proximal "hub" for fluidic attachment to a syringe or intravenous tubing; a straight tubular "shaft" which has a substantially uniform cross-section; a conical or tapered portion at the distal end of the straight tubular shaft portion (herein called "taper"); and a distal end or "tip". In addition, hypodermic needles have a removable cap which fits around the tip and shaft to removably frictionally engage the hub. None of these features, including the cap, increases user safety during needle use. Because it typically entails placing one's hand in front of the needle tip, the capping procedure may be so risky that many experts recommend that it not be performed (and that exposed needles be transported to containers for sharp disposal).
In preliminary evaluations at the Redding Ridge Veterinary Clinic (home veterinary office of Sally A. Kniffin, VMD), we have addressed the types of needle usage for which a sharp point, an open tip, and/or an exposed tip are needed. These issues are addressed in Table 1. Summarizing Table 1, a sharp point would be required to pierce the skin or a blood vessel, but not necessarily to pierce a penetrable diaphragm. An open tip might be desirable for an intramuscular injection. Otherwise (and perhaps even in the case of intramuscular injection) a recessed side opening would be sufficient.
We also have assessed whether a retractable sheath or retractable cap could be employed in these settings. Such modifications are being introduced in the present disclosure for use with our inventive series of needles. Consistent with our aim, these modifications are designed to increase user safety. Their introduction is made practical by the inventive needles, which have solid tips and therefore avoid coring.
Prior solid tip needles with recessed orifices are known, as set out below. However, the methods and series of needles disclosed herein, as well as needle/catheter combinations, means of securement, protective sheaths and retractable needle caps, have features specifically adapted for minimizing disease transmission by used hypodermic needles. More particularly, we have optimized the shaft, taper and tip of the needle, modified overlying catheters, and introduced means of covering with specially designed sheaths and caps. The disclosed methods provide unprecedented protection for the healthcare worker and a family of inventive needles which carry out the disclosed methods.
The following patent references (U.S. unless noted otherwise) disclose background types of recessed-orifice devices: Leiter U.S. Pat. No. 145,217; Mitchell and Gillespie U.S. Pat. No. 561,059; Gillman U.S. Pat. No. 1,526,595; Weyl 446,818 (German); Peterson U.S. Pat. No. 2,097,039; Hanson U.S. Pat. No. 2,634,726; Gewecke U.S. Pat. No. 2,862,495; Morgan 1,196,601 (French); Schofield U.S. Pat. No. 3,181,336; Guttman U.S. Pat. No. 3,509,880; Jamshidi U.S. Pat. No. 3,882,849; Choksi U.S. Pat. No. 4,058,121; Sampson U.S. Pat. No. 4,190,048; Galindo U.S. Pat. No. 4,411,657; Guttman U.S. Pat. No. 4,413,993; Johnson U.S. Pat. No. 4,710,180; Sprotte 3,020,926 (German); Foran U.S. Pat. No. 4,767,407. Hanson (U.S. Pat. No. 2,634,726) discloses a needle with a chisel-like point and a single recessed orifice which opens obliquely on the side of the shaft ipsilateral of the convex side of the needle point and is said to minimize the likelihood of clogging the needle and reinjecting a cork or rubber core into a patient. These references disclose one or more of the following objectives: (1) to avoid coring of a rubber diaphragm by an open-bevel needle; (2) to minimize trauma to a patient's tissues; (3) to decrease the likelihood of intraneural injections; (4) to provide an additional orifice to allow venting; and (5) to provide a special needle hub. None discloses the specific features and methods of this invention which increase user safety.
Since 1980, there have been several adaptations and modifications of recessed-orifice types of design. In 1983, Galindo (U.S. Pat. No. 4,411,657) disclosed a needle with a solid tapered tip and recessed orifice introduced to decrease nerve trauma during injection of local anesthetic. In that same year, Guttman (U.S. Pat. No. 4,413,993) claimed his recessed-orifice needle for minimizing infiltration from the cannulated vessel during intravenous infusion of fluid (even if the tip of the needle extended beyond the back wall of the vessel). In 1985, Alchas (U.S. Pat. No. 4,537,593) introduced a recessed-orifice needle with an overlying sleeve to allow venting during transfer of liquid to or from a container. In 1987, Johnson (U.S. Pat. No. 4,710,180) described a blunt-tipped cannula with multiple recessed orifices for injecting fat cells into the skin after an incision was made to allow cannula insertion. In 1987, Sprotte (German 3,020,926) introduced a modified recessed-orifice needle for regional anesthesia with improved flow characteristics and a lesser incidence of dural tear and postspinal headache.
None of these references discloses features or methods which increase user safety, as will be detailed in the ensuing description.